Embodiments of the present invention relate to a process kit for a substrate processing chamber.
In the manufacture of integrated circuits and displays, a substrate such as a semiconductor wafer or display panel, is placed in a substrate processing chamber and processing conditions are set in the chamber to deposit or etch material on the substrate. A typical process chamber comprises chamber components that include an enclosure wall that encloses a process zone, a gas supply to provide a process gas in the chamber, a gas energizer to energize the process gas to process the substrate, a gas exhaust to remove spent gas and maintain a gas pressure in the chamber, and a substrate support to hold the substrate. Such chambers can include, for example, sputtering (PVD), chemical vapor deposition (CVD), and etching chambers. In PVD chambers, a target is sputtered by energized gas to sputter target material which then deposits on the substrate facing the target.
In sputtering processes, the material sputtered from the target also deposits on the edges of chamber components surrounding the target which is undesirable. The peripheral target regions have a dark-space region in which sputtered material redeposit as a result of ion scattering in this area. Accumulation and build-up of the sputtered material in this region is undesirable as such accumulated deposits require disassembly and cleaning or replacement of the target and surrounding components, can result in plasma shorting, and can cause arcing between the target and the chamber wall. These deposits also often debond and flake off due to thermal stresses to fall inside and contaminate the chamber and its components.
A process kit comprising a shield, cover ring and deposition ring arranged about the substrate support and chamber sidewalls, is often used to receive excess the sputtered material to protect and prevent deposition on the chamber walls and other component surfaces. Periodically, the process kit components are dismantled and removed from the chamber for cleaning off accumulated deposits. Thus it is desirable to have process kit components which are designed to receive and tolerate ever larger amounts of accumulated deposits without sticking to each other or to the substrate, or resulting in flaking off of the deposits between process clean cycles. It is further desirable to have a process kit comprising fewer parts or components, as well as having components that are shaped and arranged in relationship to one another to reduce the amounts of sputtered deposits formed on the internal surfaces of the process chamber.
Another problem arises when the chamber liners and shields heat up to excessively high temperatures due to exposure to the sputtering plasma in the chamber and poor thermal conductivity between the shield and chamber components. For example, it is difficult to control the temperature of shields made of low thermal conductivity material. The thermal resistances at contact interfaces with supporting components, such as adapters, also affect shield temperatures. Low clamping forces between the shield and adapter can also give rise to heating up of the shield. Without thermal control, the temperature of the shields cycles between idle room-temperature conditions and high temperatures during sequential substrate processing. When process deposits of high-stress metal are deposited onto the shields and subjected to large temperature swings, the adhesion of the film to the shield as well as the cohesion of the film to itself, can decrease dramatically due to, for example, a mismatch of the coefficients of thermal expansion between the film and the underlying shield. it is desirable to reduce the temperatures of shields and liners during substrate processing to reduce flaking of accumulated deposits from the shield surfaces.
Another problem with conventional substrate processing chamber and PVD processes arises due to poor gas conductance from the chamber, A high-conductance gas flow pathway is needed to both supply the necessary process gasses to the process cavity and to properly exhaust spent process gas. However, the shields and other chamber components of the process kit that line the chamber walls can substantially reduce gas conductance flows. Placing apertures in these components while increasing gas conductance therethrough, also allow line-of-sight sputtering deposits to exit the process zone through the gas conductance holes to deposit on the chamber walls. Such holes can also cause plasma leakage from within the processing cavity to surrounding chamber regions. Also, chamber components that incorporate such holes have other shortcomings including, but not limited to, requirement of additional parts, their relative flimsiness, tolerance stack-ups of multiple parts, and poor thermal conductivity at interfaces.
Thus it is desirable to have process kit components that increase thermal conductivity while reducing the flaking of process deposits from component surfaces. It is further desirable to control the temperature of the shields and liners so that they do not cycle between excessively high and low temperatures during plasma processing. It is also desirable to increase overall gas conductance while preventing line-of-sight deposition outside the process zone and reduce plasma leakage.